JP2019171922A - Steering unit - Google Patents

Abstract

To provide a steering unit capable of properly sustaining backlash of a worm gear.SOLUTION: A steering unit 1 includes a worm shaft 111 on which a worm gear 110 that is meshed with a worm wheel 120 disposed on a rotation shaft 22 which drives a steering rack is formed, a motor 81 that drives the worm shaft, a bearing 210 that bears an end 112 of the worm shaft so that the end can rotate, a bearing holder 220 that accommodates the bearing so that the bearing can move, and constraining means 230 that constrains the bearing to move. The worm shaft incurs reaction forces Fr and Fl in first and second directions respectively, which are oblique to a constraining direction, when the worm wheel is driven. The bearing holder has a jut 226, which juts out to the bearing, formed in an area between the first and second directions when seen from a rotation center axis.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a steering device provided in a vehicle such as an automobile.

In a steering apparatus provided in a vehicle such as an automobile, an electric power steering apparatus that applies an assist torque by an electric motor has become widespread.
As such an electric power steering device, a pinion assist type is known in which a pinion shaft provided with a pinion gear constituting a rack and pinion mechanism is driven by a motor.
In a pinion assist type electric power steering device, there is a worm wheel provided on a pinion shaft as a reduction gear train, and a worm shaft that is engaged with the worm wheel and that is connected to an output shaft of a motor. Are known.
The worm shaft is provided with an urging means such as a spring element for urging the worm wheel toward the worm wheel so as to apply an appropriate preload so that backlash at the meshing portion with the worm wheel is appropriate.

  As a conventional technique related to the worm shaft bias and the worm gear preload of the electric power steering apparatus described above, for example, Patent Document 1 discloses a bearing at the end of the worm shaft in order to improve the steering feeling while adjusting the backlash of the gear. An elastic member formed in an arc shape is provided in the housing that holds the bearing, and the bearing is urged toward the worm wheel by the elastic member, and the bearing moves in a direction away from the worm wheel while holding the worm shaft. When the elastic member is deformed to expand or contract, the bearing is urged toward the worm wheel.

  In addition, the reaction force that the worm gear receives from the worm wheel is caused by the rotation direction (steering direction) due to the worm wheel meshing with the worm wheel while the rotation axis of the worm shaft is inclined with respect to the plane orthogonal to the rotation axis of the worm wheel. Since the direction differs depending on the position, Patent Document 2 discloses that the direction of the urging force of the coil spring in the holder member is rotated to one side in order to improve the steering feeling while adjusting the backlash of the gear. It is described that the structure is provided so as to be positioned between the direction of the reaction force received from the worm wheel and the direction of the reaction force received from the worm wheel when the worm shaft rotates to the other side.

JP 2010-218991 A JP, 2006-182888, A

As described above, since the direction of the reaction force that the worm shaft receives from the worm wheel varies depending on the rotation direction, the displacement direction of the worm shaft from the neutral position differs between the right turning and the left turning, When these trajectories are viewed from the axial direction of the worm shaft, they are substantially V-shaped bent at the neutral position.
However, for example, when the steering is immediately turned from the right turning to the left turning, the worm shaft does not pass the V-shaped trajectory passing through the neutral position, and the right turning position from the right turning position. It may show the behavior of moving to a straight line.
Also, when the steering angle is switched back from the steered state to the straight traveling state, the trajectory may return to the neutral position through a trajectory different from the trajectory when the rudder angle is increased.
In such a case, there is a concern that the preload is temporarily insufficient at the meshing position of the worm gear and the worm wheel, the backlash becomes excessive, abnormal noise is generated, and the steering feeling is deteriorated.
In view of the above-described problems, an object of the present invention is to provide a steering device that can appropriately maintain the backlash of the worm gear portion.

The present invention solves the above-described problems by the following means.
According to a first aspect of the present invention, there is provided a worm wheel provided on a rotating shaft that drives a steering rack, a worm shaft formed with a worm gear that meshes with the worm wheel, a motor that rotationally drives the worm shaft, and the worm A bearing that rotatably supports an end of the shaft opposite to the motor side; a bearing holder that movably accommodates the bearing within a predetermined movable range in a plane perpendicular to the rotation center axis; and the bearing An urging means for urging the worm gear toward the side pressed by the worm wheel, wherein the worm shaft is urged according to a turning direction when the worm wheel is driven. In the first direction and the second direction inclined with respect to the urging direction by The bearing holder is formed with a protrusion protruding toward the bearing in an intermediate region between the first direction and the second direction when viewed from the rotation center axis of the bearing. Is a steering device.
According to this, when the worm shaft displaced by the reaction force in the first direction or the second direction returns to the neutral position, the protrusion of the bearing holder guides the bearing, thereby stabilizing the locus of the worm shaft. It can be made.
For this reason, even at the time of turning back or turning back, an appropriate preload is applied to the meshing part of the worm gear with the worm wheel, and an appropriate backlash is maintained, thereby deteriorating the steering feeling and abnormal noise. Occurrence can be prevented.

According to a second aspect of the present invention, when the bearing is displaced in the first direction with respect to the bearing holder, the first pressing that presses the bearing in a direction substantially opposite to the first direction. Means and second pressing means for pressing the bearing in a direction substantially opposite to the second direction when the bearing is displaced in the second direction with respect to the bearing holder. The steering apparatus according to claim 1.
According to this, when the worm shaft displaced by the reaction force in the first direction or the second direction returns to the neutral position, the first pressing means or the second pressing means pushes the bearing back to the neutral position. By this, the trajectory along which the worm shaft moves can be further stabilized.

The invention according to claim 3 is characterized in that a concave curved guide surface portion for guiding the outer peripheral surface portion of the bearing to the protruding end side of the protruding portion is formed at both ends of the protruding portion in the circumferential direction of the bearing holder. The steering apparatus according to claim 1 or 2.
According to this, the friction at the time of a bearing climbing on a protrusion part is reduced, the movement of a bearing is made smooth, and the above-mentioned effect can be obtained more reliably.

According to a fourth aspect of the present invention, there is provided a worm wheel provided on a rotating shaft that drives a steering rack, a worm shaft formed with a worm gear that meshes with the worm wheel, a motor that rotationally drives the worm shaft, and the worm A bearing that rotatably supports an end of the shaft opposite to the motor side; a bearing holder that movably accommodates the bearing within a predetermined movable range in a plane perpendicular to the rotation center axis; and the bearing An urging means for urging the worm gear toward the side pressed by the worm wheel, wherein the worm shaft is urged according to a turning direction when the worm wheel is driven. In the first direction and the second direction inclined with respect to the urging direction by And when the bearing is displaced in the first direction with respect to the bearing holder, the first pressing means presses the bearing in a direction substantially opposite to the first direction, and the bearing And a second pressing means for pressing the bearing in a direction substantially opposite to the second direction when the bearing is displaced in the second direction with respect to the bearing holder. Device.
According to this, when the worm shaft displaced by the reaction force in the first direction or the second direction returns to the neutral position, the first pressing means or the second pressing means pushes the bearing back to the neutral position. Thus, the trajectory along which the worm shaft moves can be stabilized.
For this reason, it is possible to prevent deterioration of steering feeling and generation of abnormal noise by applying an appropriate preload to the worm gear portion and maintaining appropriate backlash even at the time of switching back or at the time of switching back.

  As described above, according to the present invention, it is possible to provide a steering device that can appropriately maintain the backlash of the worm gear portion.

It is a figure showing typically composition of a 1st embodiment of a steering device to which the present invention is applied. It is the figure which looked at the meshing part of the worm gear and the worm wheel from the radial direction of the worm gear in the steering device of the first embodiment. It is the figure which looked at the support part of the front-end | tip part of the worm shaft from the axial direction of the worm gear in the steering device of 1st Embodiment. It is sectional drawing which shows the structure of the alignment mechanism of the steering apparatus of 1st Embodiment. It is the external appearance perspective view which looked at the alignment mechanism of the steering device of 1st Embodiment from the worm gear side. It is a schematic diagram which shows the behavior of the bearing at the time of turning in the alignment mechanism of the steering apparatus which is a comparative example of this invention. It is a schematic diagram which shows the behavior of the bearing at the time of steering in the alignment mechanism of the steering device of 1st Embodiment. It is a schematic diagram which shows the behavior of the bearing at the time of steering in the alignment mechanism of 2nd Embodiment of the steering device to which this invention is applied.

<First Embodiment>
Hereinafter, a first embodiment of a steering apparatus to which the present invention is applied will be described.
A steering device 1 according to the first embodiment is provided in an automobile such as a passenger car, for example, and steers a front wheel that is a steering wheel.
The steering device 1 of the embodiment includes a pinion assist type electric power steering device as a power assist mechanism.

FIG. 1 is a diagram schematically illustrating the configuration of the steering device according to the first embodiment.
The steering device 1 includes a steering wheel 10, a steering shaft 20, an intermediate shaft 21, a pinion shaft 22, a rack shaft 30, a rack housing 40, a tie rod 50, a housing 60, a torque sensor 70, an actuator unit 80, and an electric power steering control unit. (EPS ECU) 90 and the like.

The steering wheel 10 is an annular operation member that inputs a steering operation when the driver rotates.
The steering wheel 10 is disposed facing the driver's seat in the vehicle cabin.

The steering shaft 20 is a rotating shaft having one end attached to the steering wheel 10 and transmits the rotating operation of the steering wheel 10 to a rack and pinion mechanism that converts the translational motion in the vehicle width direction. is there.
An intermediate shaft 21 and a pinion shaft 22 are sequentially connected to the end of the steering shaft 20 opposite to the steering wheel 10 side.
Between the steering shaft 20 and the intermediate shaft 21 and between the intermediate shaft 21 and the pinion shaft 22 are universal joints (cardan joints) 23 capable of transmitting rotation in a state where each axis is bent. 24 are provided.
A pinion gear that meshes with the rack gear 31 of the rack shaft 30 and drives the rack shaft 30 is formed at the tip of the pinion shaft 22.

The rack shaft 30 is a columnar member arranged such that the longitudinal direction (axial direction) is along the vehicle width direction.
The rack shaft 30 is supported so as to be able to translate in the vehicle width direction with respect to the vehicle body.
A rack gear 31 that meshes with the pinion gear of the pinion shaft 22 is formed on a part of the rack shaft 30.
The rack shaft 30 is driven by the pinion gear according to the rotation of the steering shaft 20 and is translated (straight) along the vehicle width direction.
The rack gear 31 is arranged offset to either the left or right (usually the driver's seat side) in the vehicle width direction.
For example, when the vehicle is a so-called right-hand drive vehicle with the right front seat as the driver's seat, the rack gear 31 is arranged offset to the right side from the center when neutral.

The rack housing 40 is a substantially cylindrical member that accommodates the rack shaft 30 while supporting the rack shaft 30 so as to be relatively displaceable along the vehicle width direction.
Rack boots 41 are provided at both ends of the rack housing 40.
The rack boot 41 is a member that prevents intrusion of foreign matters such as dust into the rack housing 40 while allowing relative displacement of the tie rod 50 with respect to the rack housing 40.
The rack boot 41 is formed in a flexible bellows cylinder shape by using a resin material such as an elastomer.

The tie rod 50 is a shaft-like interlocking member that connects the end of the rack shaft 30 and the knuckle arm 61 of the housing 60 and rotates the housing 60 about the kingpin axis in conjunction with the translational movement of the rack shaft 30. is there.
An end portion on the inner side in the vehicle width direction of the tie rod 50 is connected to an end portion of the tie rod 30 via a ball joint 51 so as to be swingable.
The end of the tie rod 50 on the outer side in the vehicle width direction is connected to a knuckle arm 61 of the housing 60 via a ball joint 52.
A connecting portion between the tie rod 50 and the ball joint 52 is provided with a turnbuckle mechanism for toe-in adjustment.

The housing (knuckle) 60 is a member that accommodates a hub bearing that supports the wheel W so as to be rotatable around the axle.
The housing 60 has a knuckle arm 61 that protrudes forward or rearward with respect to the axle.
The housing 60 is supported so as to be rotatable around a kingpin axis that is a predetermined rotation center axis.
For example, when the front suspension of the vehicle is a McPherson strut type, the kingpin shaft connects the bearing center of the strut top mount and the center of the ball joint connecting the lower part of the housing 60 and the transverse link (lower arm). It is a virtual axis.
The housing 60 is rotated about the kingpin axis by being pushed and pulled by the rack shaft 30 through the tie rod 50 to steer the wheels W.

The torque sensor 70 is a sensor that detects torque acting on the pinion shaft 22.
The torque sensor 70 is provided in a portion of the pinion shaft 22 closer to the intermediate shaft 21 than the actuator unit 80.
The output of the torque sensor 70 is transmitted to the electric power steering control unit 90.

The actuator unit 80 is a drive device that rotationally drives the pinion shaft 22 to perform power assist during manual operation and steering operation during automatic operation.
The actuator unit 80 includes a motor 81, a gear box 82, and the like.
The motor 81 is an electric actuator that generates a driving force applied to the steering shaft 20.
The motor 81 is controlled by the electric power steering control unit 90 in the rotation direction and the output torque.
The gear box 82 includes a reduction gear train that decelerates (torque amplification) the rotational output of the motor 81 and transmits it to the pinion shaft 22.
The configuration of the gear box 82 will be described in detail later.

The electric power steering control unit 90 is a control device that gives command values for the rotational direction and output torque to the motor 81.
The electric power steering control unit 90 sets a command value given to the motor 81 based on the torque input direction of the torque sensor 70 and the detected torque value during manual operation of the vehicle.
Further, during automatic driving of the vehicle, the electric power steering control unit 90 sets a command value given to the motor 81 based on a command given from an automatic driving control device (not shown).

Hereinafter, the configuration of the gear box 82 of the actuator unit 80 will be described in more detail.
The gear box 82 includes a worm gear 110 attached to the output shaft of the motor 81 and a worm wheel 120 attached to the pinion shaft 22 as a reduction gear train.
FIG. 2 is a view of the meshing portion between the worm gear and the worm wheel as viewed from the radial direction of the worm gear.
FIG. 3 is a view of the support portion at the tip of the worm shaft as viewed from the axial direction of the worm gear.
In the first embodiment, the plane including the central axis of the worm gear 110 and the plane orthogonal to the central axis of the worm wheel 120 are arranged so as to be inclined by a predetermined angle.

The worm gear 110 is formed at an intermediate portion of a worm shaft 111 that is a cylindrical rotating shaft.
The worm gear 110 is fixed to the worm shaft 111 and rotates around the central axis together with the worm shaft 111.
One end of the worm shaft 111 (the right side in FIG. 2) is connected to the output shaft of the motor 81 and is driven by the motor 81.
The end of the worm shaft 111 on the motor 81 side is supported by a bearing 112.
The outer ring of the bearing 112 is incorporated in the gear box case 82a and is substantially restrained.
The gear box case 82a is formed, for example, by casting a rough shape with a metal material such as an aluminum alloy and performing predetermined machining.
The other end of the worm shaft 111 (on the side opposite to the motor 81) is supported by the alignment mechanism 200 described below so as to be relatively displaceable along a plane perpendicular to the central axis with respect to the gear box case 82a.

FIG. 4 is a cross-sectional view showing the configuration of the alignment mechanism of the steering device according to the first embodiment.
FIG. 4A is a cross-sectional view of the alignment mechanism viewed along the rotation center axis of the worm shaft 111.
FIG. 4B is a cross-sectional view taken along the line bb in FIG.
The alignment mechanism 200 includes a bearing 210, a bearing holder 220, a spring 230, a holder case 240, an O-ring 250, and the like.

The bearing 210 rotatably supports the journal portion 113 provided at the protruding end portion of the worm shaft 111.
As the bearing 210, for example, a single row deep groove ball bearing can be used.

The bearing holder 220 is a cup-shaped member that houses the bearing 210.
The bearing holder 220 is integrally formed, for example, by injection molding a resin material.
The bearing holder 220 includes a cylindrical portion 221, an end surface portion 222, a spring locking portion 223, a groove portion 224, a protrusion 225, a guide portion 226, and the like.

The cylindrical portion 221 is a substantially cylindrical portion in which the bearing 210 is accommodated.
The inner diameter of the cylindrical portion 221 is set to be larger than the outer diameter of the bearing 210, and the inner peripheral surface of the cylindrical portion 221 is disposed to face the outer peripheral surface of the outer ring of the bearing 210.
The bearing 210 can be relatively displaced with respect to the bearing holder 220 within a plane orthogonal to the central axis on the inner diameter side of the cylindrical portion 221.

The end surface portion 222 is a flat plate-like portion that is provided at an end portion of the cylindrical portion 221 opposite to the worm gear 110 side and is disposed along a plane orthogonal to the central axis of the worm shaft 111.
A circular opening that accommodates the protruding end portion of the worm shaft 111 is provided at the center of the end surface portion 222.

The spring locking portion 223 is a portion where a part of the spring 230 is locked.
The spring locking portion 223 is provided on a part of the circumference of the cylindrical portion 221.
The spring locking portion 223 is arranged on the side of the preload Fp (see FIG. 3) acting direction (worm gear 120 side) of the spring 230 when viewed from the center of the cylindrical portion 221.

The groove portion 224 is a circumferential groove formed in a region near the end surface portion 222 on the outer peripheral surface of the bearing holder 220.
The groove portion 224 has a substantially rectangular groove cross-sectional shape, and is continuously formed over the entire circumference along the circumferential direction of the cylindrical portion 221.
The O-ring 250 is accommodated in the groove portion 224.

The protrusion 225 is formed so as to protrude from a part of the end surface portion 222 to the side opposite to the motor 81 side.
The protrusion 225 is inserted into the opening 243 of the holder cover 240 and functions as a positioning unit that restricts relative rotation of the bearing holder 220 with respect to the holder cover 240.

The guide portion 226 is a protruding portion that is formed so as to protrude from the portion facing the outer peripheral surface of the bearing 210 on the inner peripheral surface of the cylindrical portion 221 of the bearing holder 220 to the inner diameter side (bearing 210 side).
The guide portion 226 is provided on the side opposite to the biasing direction by the spring 230 (the direction in which the spring locking portion 223 is provided when viewed from the central axis of the bearing 210).
The detailed shape of the guide part 226 will be described in detail later.

The spring 230 is a biasing means that biases the bearing 210 in a direction in which the worm gear 110 is pressed against the worm wheel 120 to give a preload.
As the spring 230, for example, a coil spring (winding spring) obtained by winding a wire made of spring steel on the outer diameter side of the bearing 210 can be used.
A part of the spring 230 on the circumference is locked to the spring locking portion 223 of the bearing holder 220.
A part of the periphery of the spring 230 opposite to the spring locking portion 223 side is disposed so as to be in pressure contact (pressing) with the outer peripheral surface of the outer ring of the bearing 210.
The spring 230 urges the bearing 210 to the spring locking portion 223 side by its elastic force, and preload is applied to the meshing position between the worm gear 110 and the worm wheel 120 by this urging force.

The holder case 240 is a cup-shaped member that houses the bearing holder 220.
The holder case 240 is formed by, for example, sheet metal processing using a metal plate.
The holder case 240 is fixed to the gear box case 82a in a state where the relative positional relationship between the motor 81 and the worm wheel 120 is substantially fixed.

The holder case 240 has a cylindrical portion 241 and an end surface portion 242.
The cylindrical part 241 is formed in a substantially cylindrical shape.
The inner peripheral surface of the cylindrical portion 241 is disposed to face the outer peripheral surface of the cylindrical portion 221 of the bearing holder 220 with a space therebetween.

The end surface portion 242 is provided at an end portion of the cylindrical portion 241 opposite to the motor 81 side.
The end surface portion 242 has a flat plate shape extending substantially along a plane substantially orthogonal to the central axis of the worm shaft 111.
An opening 243 into which the protrusion 225 of the bearing holder 220 is inserted is formed in the end surface portion 242.
At the peripheral edge of the opening 243, a flange protruding to the opposite side to the cylindrical portion 241 side is formed.

The O-ring 250 is an annular member that is formed of an elastic material such as a rubber material and has a substantially circular cross-sectional shape.
The O-ring 250 is fitted in the groove 224 of the bearing holder 220 over the circumferential direction.
In this state, a part of the O-ring 250 projects from the outer peripheral surface of the bearing holder 220.
The O-ring 250 has a function of holding the bearing holder 220 by its elastic force when the bearing holder 220 is inserted into the holder case 240.

The worm gear 110 described above receives the reaction forces Fr and Fl on the other tooth surfaces when the steering wheel is turned to the right and when the steering wheel is turned to the left at the meshing position Pm shown in FIG.
Here, it is assumed that the worm shaft 111 rotates around the center Cb of the bearing 112 when a load is input.
In this case, the component force differs because the moment spans MSr and MSl at the time of the right turn and the left turn are different from the offset amount between the load input position (meshing position Pm) and the fulcrum (center Cb).
The main factors affecting the component force direction include the offset amount between the load point (engagement position Pm) and the center Cb of the bearing 112, the twist angle of the worm shaft 111, the axial distance of the worm shaft 111, and the like.

As shown in FIG. 3, when viewed from the axial direction of the worm shaft 111, the reaction force Fr when turning right and the reaction force Fl when turning left are both in the direction in which the worm shaft 111 moves away from the worm wheel 120. There are, however, acting in directions in which the angles are inclined to each other.
The preload Fp by the spring 230 acts in a direction in which the worm shaft 111 is brought closer to the worm wheel 120 along a straight line arranged in the middle of the straight lines along the acting directions of the reaction forces Fr and Fl.

Hereinafter, the effect of the first embodiment described above will be described in comparison with a comparative example of the present invention described below.
Note that, in the comparative example and the second embodiment to be described later, portions that are substantially the same as those in the first embodiment described above are denoted by the same reference numerals and description thereof is omitted.
In the steering device of the comparative example, the guide portion 226 of the bearing holder 220 in the first embodiment is omitted.

FIG. 6 is a schematic diagram showing the behavior of the bearing at the time of turning in the alignment mechanism of the steering device which is a comparative example of the present invention.
In FIG. 6, for easy understanding, the interval between the outer peripheral surface of the bearing 210 and the inner peripheral surface of the bearing holder 220 is exaggerated. (The same applies to FIGS. 7 and 8 to be described later)
When the steering is in the neutral state, the central axis of the bearing 210 is located at the neutral position P0.
The spring 230 biases the worm shaft 111 upward in FIG. 6 so that the preload between the worm gear 110 and the worm wheel 120 is appropriate at the neutral position P0.

When the steering is steered to the right from the neutral state, the central axis of the bearing 210 is substantially straight along the locus T1 to the position Pr when turning right by the reaction force Fr received from the tooth surface by the worm gear 110. Displace.
On the other hand, when the steering is turned to the left from the neutral state, the central axis of the bearing 210 is substantially linear along the locus T2 due to the reaction force Fl received by the worm gear 110 from the tooth surface. Displace to Pl.

When returning from the right-turned state to the neutral position and when returning from the left-turned state to the neutral position, ideally, the position of the central axis of the bearing 210 is linear along the trajectories T3 and T4. It is preferable to return to the neutral position P0.
However, in practice, there is a case where the trajectory returns to the neutral position P0 along the trajectory T5 which is deviated from the trajectory T1 and is bent and curved.
Further, for example, in the situation of turning from the right-turned state to the left-turned state, there is a case where the right-turning position Pr moves to the left-turning position Pl along the linear locus T6 without passing through the neutral position P0. .
6 to 8, the trajectories T1 to T6 are exaggerated with respect to the actual movement distance of the central axis of the bearing 210 for easy understanding.
In the comparative example, as a result of the variation in the trajectory along which the central axis of the bearing 210 moves as described above, the engagement state may be deteriorated due to insufficient preload, and noise may be generated, or the steering feeling may be deteriorated. Furthermore, there is a problem that the reproducibility of such a phenomenon is poor.

On the other hand, in 1st Embodiment, it has the guide part 226 which made the internal peripheral surface of the bearing holder 220 protrude on the opposite side to the preload direction seeing from the neutral position P0.
A central portion 226a of the guide portion 226 in the circumferential direction of the bearing holder 220 has a convex curved surface that is convex on the bearing 210 side.
The protruding end portion (the portion located closest to the inner diameter side of the bearing holder 220) in the central portion 226a is disposed on the side opposite to the preload direction when viewed from the neutral position P0 of the central axis of the bearing 210.
Further, both end portions 226b (regions sandwiching the central portion 226a) of the guide portion 226 in the circumferential direction of the bearing holder 220 have a curvature that is substantially along the outer peripheral surface of the bearing 210, and are concave curved surfaces that are recessed on the bearing 210 side. ing.

In the first embodiment, when the steering is turned back from the state in which the bearing 210 is at the position Pr when turning right, the outer peripheral surface of the bearing 210 extends along the inner peripheral surface of the cylindrical portion 221 of the bearing holder 220. When contacting the guide part 226 while sliding in the clockwise direction in FIG. 7, the central axis is guided to move toward the neutral position P0 along the surface shape of the guide part 226.
Further, substantially the same behavior is exhibited when switching back from the left-cut state.
As a result, the trajectories T3 and T4 of the center axis of the bearing 210 when the steering is switched back from the steered state approach and stabilize the trajectories T1 and T2 when the steering is increased.
Even in a situation where the steering is turned from right steering to left steering, or from left steering to right steering, the vicinity of the neutral position P0 is once passed.
As a result, the preload at the meshing position between the worm gear 110 and the worm wheel 120 can be properly maintained, and the generation of abnormal noise and the deterioration of the steering feeling can be prevented.

As described above, according to the first embodiment, the following effects can be obtained.
(1) The worm shaft 111 is moved by the reaction forces Fr and Fl when turning right and left, and the center axis of the bearing 210 is moved to the position Pr when turning right and the position Pl when turning left, and then the spring 230 When returning to the neutral position P0 by the urging force, the outer peripheral surface of the bearing 210 moves the bearing 210 along the surface of the guide portion 226 and guides the bearing 210, thereby stabilizing the trajectory of the worm shaft 111 moving. Can be made.
For this reason, an appropriate preload is applied to the meshed portion of the worm gear 110 and the worm wheel 120 even when the reversing or reversing is performed when the magnitude of the reaction force and the direction of action are changed, thereby maintaining an appropriate backlash. The deterioration of the steering feeling and the generation of abnormal noise can be prevented.
(2) By making both end portions 226b of the guide portion 226 in the circumferential direction of the bearing holder 220 into a concave curved surface, the friction when the bearing 210 rides on the guide portion 226 is reduced, and the movement of the bearing 210 is made smooth. The effect can be obtained more reliably.

<Second Embodiment>
Next, a second embodiment of the steering device to which the present invention is applied will be described.
FIG. 8 is a schematic diagram illustrating the behavior of the bearing during turning in the alignment mechanism of the steering device according to the second embodiment.
In the second embodiment, instead of the guide portion 226 of the first embodiment, a pair of guide portions 260 and 270 are provided between the inner peripheral surface of the cylindrical portion 221 of the bearing holder 220 and the outer peripheral surface of the bearing 210. It is provided.
For example, the guide portions 260 and 270 can be formed in a tab shape protruding from the end surface portion 222 of the bearing holder 220 toward the motor 81 side.
The guide portions 260 and 270 can be formed integrally with the bearing holder 220 by using, for example, an elastic resin material.
When the central axis of the bearing 210 is displaced to the position Pr at the right turn and the position Pl at the left turn, the guide portions 260 and 270 press the outer peripheral surface of the outer ring of the bearing 210 in a direction to push back to the neutral position P0 side. It is a pressing means.

As shown in FIG. 8, the guide portion 260 is provided at a position where the guide shaft 260 comes into contact with the outer peripheral surface of the bearing 210 when the central axis of the bearing 210 moves from the neutral position P0 to the position Pr when turning right.
The guide portion 270 is provided at a location where the center axis of the bearing 210 comes into contact with the outer peripheral surface of the bearing 210 when the center axis moves from the neutral position P0 to the left-turned position Pl.
In the guide portions 260 and 270, the surface portion that comes into contact with the outer peripheral surface of the bearing 210 is formed as a concave curved surface having a circular arc shape when viewed from the axial direction of the bearing 210.

  When the guide portions 260 and 270 come into contact with the outer peripheral surface of the bearing 210, the guide portions 260 and 270 are bent in a direction close to the inner peripheral surface of the cylindrical portion 221 of the bearing holder 220 due to the contact load, and by the reaction force generated by the elastic force. The effect of pushing the bearing 210 back to the neutral state is exhibited.

  Also in the second embodiment described above, when the center axis of the bearing 210 is moved to the position Pr at the right turn and the position Pl at the left turn by the reaction forces Fr and Fl at the right turn and the left turn, By pushing the bearing 210 back to the neutral position side by the elastic force generated by the bending of the guide portions 260 and 270, substantially the same effect as that of the first embodiment described above can be obtained.

(Modification)
The present invention is not limited to the embodiments described above, and various modifications and changes are possible, and these are also within the technical scope of the present invention.
(1) The configuration of the power steering device, its electric power assist mechanism, the worm shaft alignment mechanism, and the like is not limited to the configuration of the above-described embodiment, and can be changed as appropriate.
For example, the electric power assist mechanism of the embodiment is of a pinion assist type that drives a pinion shaft as an example, but the present invention is a steering device having another type of electric power assist mechanism such as a column assist type. Even if it exists, it is possible to apply as long as it uses a worm gear and a worm wheel.
(2) It is good also as a structure which provides together the protrusion-shaped guide part like 1st Embodiment, and the guide part which has a press means like 2nd Embodiment in the same bearing holder.
(3) In the second embodiment, the guide portion (pressing means) is configured to generate the restoring force of the bearing by its own elasticity. For example, the guide portion is biased by a spring element such as a coil spring. It is good.

DESCRIPTION OF SYMBOLS 1 Steering device 10 Steering wheel 20 Steering shaft 21 Intermediate shaft 22 Pinion shaft 23 Universal joint 24 Universal joint 30 Rack shaft 31 Rack gear 40 Rack housing 41 Rack boot 50 Tie rod 51 Ball joint 52 Ball joint 60 Housing 61 Knuckle arm 70 Torque sensor 80 Actuator unit 81 Motor 82 Gear box 90 Electric power steering control unit 110 Worm gear 111 Worm shaft 112 Bearing 113 Journal part 120 Worm wheel 200 Aligning mechanism 210 Bearing 220 Bearing holder 221 Cylindrical part 222 End face part 223 Spring locking part 224 Groove 225 Projection 226 Guide part 226a Center part 226b Both ends 230 Spring 240 Holder case 241 Cylindrical part 242 End face part 243 Opening 250 O-ring 260 Guide part 270 Guide part T1 to T6 Trajectory of bearing central axis P0 Neutral position of bearing central axis Pr Position when the bearing center shaft is turned to the right Pl Position when the bearing center shaft is turned to the left Pm Engagement position Fp Preload Fr Reaction force when turning right Fl Reaction force when turning left MSr Moment span when turning right MSl When turning left Moment span

Claims (4)

A worm wheel provided on a rotating shaft that drives the steering rack;
A worm shaft formed with a worm gear meshing with the worm wheel;
A motor that rotationally drives the worm shaft;
A bearing that rotatably supports an end of the worm shaft opposite to the motor,
A bearing holder for accommodating the bearing movably within a predetermined movable range in a plane orthogonal to the rotation center axis;
A urging means for urging the bearing toward a side where the worm gear is pressed against the worm wheel,
The worm shaft receives a reaction force in the first direction and the second direction inclined with respect to the urging direction by the urging means according to the turning direction when the worm wheel is driven,
The steering wheel characterized in that the bearing holder has a protruding portion protruding toward the bearing in an intermediate region between the first direction and the second direction when viewed from the rotation center axis of the bearing. apparatus. First pressing means for pressing the bearing in a direction substantially opposite to the first direction when the bearing is displaced in the first direction with respect to the bearing holder;
And a second pressing means for pressing the bearing in a direction substantially opposite to the second direction when the bearing is displaced in the second direction with respect to the bearing holder. The steering apparatus according to claim 1. The concave curved guide surface portion that guides the outer peripheral surface portion of the bearing to the protruding end side of the protruding portion is formed at both ends of the protruding portion in the circumferential direction of the bearing holder. 2. The steering device according to 2. A worm wheel provided on a rotating shaft that drives the steering rack;
A worm shaft formed with a worm gear meshing with the worm wheel;
A motor that rotationally drives the worm shaft;
A bearing that rotatably supports an end of the worm shaft opposite to the motor,
A bearing holder for accommodating the bearing movably within a predetermined movable range in a plane orthogonal to the rotation center axis;
A urging means for urging the bearing toward a side where the worm gear is pressed against the worm wheel,
The worm shaft receives a reaction force in the first direction and the second direction inclined with respect to the urging direction by the urging means according to the turning direction when the worm wheel is driven,
First pressing means for pressing the bearing in a direction substantially opposite to the first direction when the bearing is displaced in the first direction with respect to the bearing holder;
And a second pressing means for pressing the bearing in a direction substantially opposite to the second direction when the bearing is displaced in the second direction with respect to the bearing holder. Steering device.

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